Water heating accounts for 20% or more of an average household’s annual energy expenditures. The yearly operating costs for conventional gas or electric storage tank water heaters average $300 or $550, respectively. Storage tank type water heaters raise and maintain the water temperature to the temperature setting on the tank (usually between 120 -140° F. Even if no hot water is drawn from the tank (and cold water enters the tank), the heater will operate periodically to maintain the water temperature. This is due to "standby losses": the heat conducted and radiated from the walls of the tank and in gas fired water heaters through the flue pipe. These standby losses represent 10% to 20% of a household’s annual water heating costs. One way to reduce this expenditure is to use a tankless or demand water heater. Here at Joe Mumford Plumbing & Heating Co., Noritz Tankless Water Heaters have proven itself to be the superior choice of Professionals.
Tankless water heaters are common in Japan and Europe. They began appearing in the United States about 25 years ago. Unlike "conventional" tank water heaters, tankless water heaters heat water only as it is used, or on demand. A tankless unit has a heating device that is activated by the flow of water when a hot water valve is opened. Once activated, the heater delivers a constant supply of hot water. The output of the heater, however, limits the rate of the heated water flow.
Gas and Electric Tankless Water Heaters
Tankless water heaters are available in propane (LP), natural gas, or electric models, (although, because of utility rates, electric isn’t advisable here in California). They come in a variety of sizes for different applications, such as a whole house water heater, a hot water source for a remote bathroom or hot tub, or as a boiler to provide hot water for a home heating system. They can also be used as a booster for dishwashers, washing machines, and a solar or wood fired domestic hot water system.
You may install a demand water heater centrally or at the point of use, depending on the amount of hot water required. For example, you can use a small electric unit as a booster for a remote bathroom or laundry. These are usually installed in a closet or underneath a sink. The largest gas units, which may provide all the hot water needs of a household, are installed centrally. Gas fired models have a higher hot water output than electric models. As with many tank water heaters, even the largest whole house tankless gas models cannot supply enough hot water for simultaneous, multiple uses of hot water (i.e., showers and laundry). Large users of hot water, such as the clothes washer and dishwasher, may need to be operated independently of each other. Alternatively, separate demand water heaters can be installed to meet individual hot water loads, or two or more water heaters can be connected in parallel for simultaneous demands for hot water.
Selecting a Tankless Water Heater
Select a Noritz Tankless Water Heater based on the maximum amount of hot water to meet your peak demand. Use the following assumptions on water flow for various appliances to find the size of unit that is right for your purposes:
Faucets: 0.75 gallons to 2.5 gallons per minute.
Low-flow shower heads: 1.2 gallons to 2 gallons per minute.
Older standard shower heads: 2.5 gallons to 3.5 gallons per minute.
Clothes washers and dishwashers: 1 gallon to 2 gallons per minute.
Unless you know otherwise, assume that the incoming potable water temperature is 50 F You will want your water heated to 120° F for most uses, or 140° F for dishwashers without internal heaters. To determine how much of a temperature rise you need, subtract the incoming water temperature from the desired output temperature. In this example, the needed rise is 70 F
List the number of hot water devices you expect to have open at any one time, and add up their flow rates. This is the desired flow rate for the demand water heater. Select a model of Noritz Tankless Water Heaters that is closest to your needs.
As an example, assume the following conditions: One hot water faucet open with a flow rate of 0.75 gallons per minute and one person bathing, using a shower head with a flow rate of 2.5 gallons per minute. Add the two flow rates together. If the inlet water temperature is 50 F the needed flow rate through the demand water heater would need to be no greater than 3.25 gallons per minute. Faster flow rates or cooler inlet temperatures will reduce the water temperature at the most distant faucet. Using low-flow shower heads and water conserving faucets are a good idea with tankless water heaters.
Noritz Tankless Water Heaters are thermostatically controlled. They can vary their output temperature according to the water flow rate and the inlet water temperature. This is useful when using a solar water heater for preheating the inlet water. If, using the above example, you connect this same unit to the outlet of a solar system, it only has to raise the water temperature a few degrees more, if at all, depending on the amount of solar gain that day.
Tankless water heaters cost more than conventional storage tank-type units. Small point-of-use heaters that deliver 1 gallon to 2 gallons per minute sell for about $400. Larger gas-fired tankless units that deliver 3 gallons to 8 gallons per minute cost $650-$2,200.
The appeal of tankless water heaters is not only the elimination of the tank standby losses and the resulting lower operating costs, but also the fact that the heater delivers hot water continuously. Noritz has an intermittent ignition device (IID). This resembles the spark ignition device on some gas kitchen ranges and ovens. Not all demand water heaters have this electrical device. You should check with the manufacturer for models that have this feature.
Even though Noritz has a 10 year warrantee, Noritz, as do most tankless models, have a life expectancy of more than 20 years. In contrast, storage tank water heaters have a 6 year warrantee and are expected to last 10 to 15 years. Most tankless models have easily replaceable parts that can extend their life by many years more.